Over the past twenty years, computer technology has evolved very rapidly. One aspect of this evolution has been a progressively growing demand for increased storage capacity in memory devices. In order to provide high storage density at a reasonable cost, one of the most enduring techniques has been to provide a rotatable hard disk that includes a layer of magnetic material, and a read/write head which is supported for movement adjacent the disk.
In arrangements of this type, if the head is exposed to airborne dust, smoke, vapors or other contaminants, these contaminants can progressively build up on the head. Eventually, the buildup becomes sufficient to interfere with the interaction between the head and disk, thereby increasing the error rate until the device will not operate. In order to avoid this problem, most hard disk drives have the disk and head disposed within a sealed enclosure, so that the head and disk are not exposed to any airborne contaminants that may happen to be present externally of the enclosure.
This approach works well where the entire hard disk drive is permanently installed in a computer. In another type of system, however, a hard disk is provided in a removable cartridge, and it is desirable that the cartridge not include the read/write head. In this regard, there are advantages to placing a head stack assembly (HSA) and its support structure within the drive which receives the cartridge, rather than in the cartridge. For example, a typical user will have several removable cartridges for each drive. Thus, in terms of overall system cost, it is cheaper to provide a single head stack assembly and support in the drive, rather than to provide several separate head stack assemblies which are each disposed in a respective one of the many cartridges used with that drive. However, this presents problems in regard to keeping the head clean.
More specifically, in order to permit the head from the drive to access the disk within the cartridge, the cartridge is not provided with a sealed enclosure of the type discussed above. Instead, the cartridge is provided with an opening through which the head of the drive can be inserted into the cartridge. In some cases, a movable shutter is provided to obstruct the opening when the cartridge is not in the drive, but the shutter is open when the cartridge is in the drive. Thus, in either configuration, when the cartridge is in the drive, the opening gives not only the head but also ambient air access to the disk and head. Consequently, any dust, smoke, vapor or other contaminant carried by the ambient air can get inside the cartridge enclosure, and the operational surface of the head can quickly develop a buildup of contaminants.
The effect of this buildup can be ameliorated to some extent by keeping the storage density of the hard disk in the removable cartridge at a relatively low level, in comparison to the levels used for hard disks located within sealed enclosures. However, as mentioned above, the commercial marketplace is exhibiting a strong and progressively increasing demand for high-density storage in a removable cartridge.
A further consideration is that existing high-density read/write heads typically have an operational surface with recesses therein. While it is not too difficult to clean the outermost portions of the operational surface of such a head, it is more difficult to clean other portions of the surface which are within the shallow recesses. As contamination collects in the recesses, it can significantly degrade system operation.